1. Field of the Invention
The invention is based on an electrical apparatus, in particular a surge arrester.
2. Discussion of Background
The invention refers to a prior art of electrical apparatuses as is specified in EP 0 564 334 A1. An electrical apparatus which is described in this prior art is preferably designed as a surge arrester or as an insulator for high-voltage or medium-voltage grid systems contains a detection and indicating apparatus which is used to monitor the electrical apparatus for a fault current. This apparatus has a dielectric housing with an easily frangible window. An electrical connection of the electrical apparatus is passed through the dielectric housing. The part of the electrical connection which is located in the housing interior is surrounded by a magnet core which is fitted with the secondary winding of a current transformer which has the electrical connection as its primary winding. The secondary winding is connected to a non-reactive resistor which is embedded in an explosive charge that is arranged in the housing interior. When a fault current occurs, the non-reactive resistor which is continuously fed with current from the current transformer is heated very severely. The resistor detonates the explosive charge above a critical limiting temperature. In the process, the window of the dielectric housing is broken open and a colored strip, which is used as an indicating element, is ejected from the housing. After tripping and after optical indication of the fault state, the electrical apparatus and the detection and indicating apparatus are removed and replaced.
In an article by R. Stierlin "Technologie-transfer fuhrt zu cleveren SAW-Tags" [Technology transfer leads to clever SAW tags], Management Zeitschrift [Management Journal] 63 (1994) No. 11, Verlag Industrielle Organisation BWIETH--Zurichbergstrasse 18, CH-8028 Zurich, information carriers (tags) are described which are attached to a mobile object, for example a vehicle or a container. When such a tag comes within the detection range of a read station, this station identifies the information carried by the tag and thus identifies the mobile object. This tag in general draws energy from a battery or from electromagnetic waves, in particular microwaves, and transmits electromagnetic waves, containing the information, to the read unit. To this end, the tag has an antenna for transmission and, possibly, for reception of electromagnetic waves as well as a semiconductor-based component which is connected to the antenna via an electrical conductor and in which data relevant to the mobile object are stored. The component may be designed as a so-called SAW tag (SAW=surface acoustic wave). It then receives microwave signals transmitted from the read unit and received via the antenna, converts these signals into acoustic signals, and thus allows analog signal processing in a minimum space. In addition, such a SAW tag does not need any internal energy source, such as a battery, but draws its energy from the power transmitted from the read unit.